just a few calcs for aggron
+6 252 Atk Mewtwo-Mega-X Drain Punch vs. 252 HP / 252+ Def Fur Coat Aggron-Mega: 254-300 (73.8 - 87.2%) -- guaranteed 2HKO
+4 252+ Atk Rayquaza-Mega V-create vs. 252 HP / 252+ Def Fur Coat Aggron-Mega: 318-376 (92.4 - 109.3%) -- 56.3% chance to OHKO


Real steel (Aggron-Mega) @ Leftovers
Ability: Fur Coat
EVs: 248 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Impish Nature
- Leech Seed
- Strength Sap
- Spectral Thief
- Meteor Mash

Bowling pin (Registeel) @ Safety Goggles
Ability: Regenerator
Shiny: Yes
EVs: 248 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Careful Nature
- Nuzzle
- U-turn
- Rapid Spin
- Toxic Spikes

Stan (Giratina) @ Toxic Orb
Ability: Poison Heal
EVs: 248 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Sassy Nature
IVs: 0 Atk
- Baneful Bunker
- Mirror Coat
- Hex
- Psycho Shift

The king (Gengar-Mega) @ Focus Sash
Ability: Merciless
EVs: 248 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Hex
- Venoshock
- Ice Beam
- Heart Swap

replacement? (Blaziken-Mega) @ Safety Goggles
Ability: Illusion
EVs: 252 HP / 252 Atk / 252 Def / 252 SpD / 252 Spe
Jolly Nature
- V-create
- Low Kick
- Thousand Arrows
- Shift Gear

Flying Stan (Giratina-Origin) @ Safety Goggles
Ability: Prankster
EVs: 248 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Sassy Nature
IVs: 0 Atk
- Sticky Web
- Hex
- Haze
- Destiny Bond